On November 14, 2002 the Center for Biological Diversity and several other conservation groups petitioned the National Marine Fisheries Service (NMFS) to designate Alaska's most imperiled orca population as a "depleted stock" under the Marine Mammal Protection Act (MMPA). The 'depleted stock' designation would mark the first time the federal government took action specifically to protect orcas in Prince William Sound.

The orca population, known to scientists as the "AT1 group," ranges from Prince William Sound to Kenai Fjords, and has dwindled from at least 22 animals to just 9 over the past 13 years. The AT1 group is genetically distinct from all other orcas, and should be managed as a separate stock.

AT1 group patrolling shores for seals.

The causes of the AT1 group's decline are uncertain, but a combination of factors is probably involved. Exposure to crude oil is one likely cause, as some members of the group were observed swimming through oil during the 1989 Exxon Valdez oil spill, and were never seen again. Underwater vessel noise, which continues to increase in Prince William Sound, is known to disrupt the whales' hunting patterns, and populations of their primary prey, harbor seals, have declined over 80 percent over the last 20 years.

Disturbingly, the Sound's orcas rank among the most contaminated marine mammals ever measured. Tissues from one AT1 group member, who stranded and died in the summer of 2000, contained 424 parts per million (ppm) of the pesticide DDT (dichlorodiphenyltrichloroethane) and 370 ppm of PCBs (polychlorinated biphenyls), a class of toxic chemicals used in pesticides and other products. This compares with Food and Drug Administration standards of 5 ppm of DDT and 2 ppm of PCB in fish for human consumption, and even exceeds levels found in Canada's heavily contaminated St. Lawrence River beluga whales.

Contaminants have been implicated in the non-recovery of those whales. NMFS is charged with managing orcas pursuant to the Marine Mammal Protection Act (MMPA), but generally takes no protective actions for particular stocks unless the stock is listed as "depleted." Despite the Alaska Regional Scientific Review Group's recommendation that it do so, NMFS has not yet designated the AT1 group as a separate stock. Instead, it has left the AT1s lumped in with a larger category of Eastern North Pacific Transients, numbering an estimated 346 animals with a range covering thousands of miles from western Alaska to California, and including animals that do not breed, hunt, or congregate together.

The Center is urging NMFS to accept the Scientific Review Group's recommendation to recognize and manage the AT1 group as a separate stock. Once recognized as such, a stock qualifies for the "depleted" classification if its population drops below its "optimum sustainable population," which the AT1 group already has done. The MMPA requires NMFS to prepare conservation plans designed to help depleted stocks recover to optimal levels.

Alaska killer whales: In response to a petition we filed in 2002, the National Marine Fisheries Service announced in May that it would designate a small group of Alaska killer whales as depleted under the Marine Mammal Protection Act. The population of these particular transient killer whales has been dwindling since some were seen swimming through oil from the 1989 Exxon Valdez spill. Scientists also their demise may also stem from the high levels of industrial contaminants, such as PCBs and DDT, that have been found in their blubber, or from the 80 percent reduction in harbor seals, a major food source for the whales. Fortunately, the depleted designation will allow the killer whales to receive federal protection and a study to determine how they can be saved from extinction.

graphic Andrew Rodman ©2002
June 24, 2004
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